Handle regex exception when comparing log

[mazimkhan]

Lines from template log are first matched literally and then as regex. In failure cases a line that is expected to match literally will not match and be tried as a regex patter. If the line has unqualified regex it may raise exception. Hence regex exception should be handled as a possibility and match() function should return False (no match) on exception.

@bridadan @adbridge Please review.

[adbridge]

@mazimkhan merge commits onto PRs are frowned upon (certainly for mbed-os) code as it makes patching hard. A rebase and force push would have been better....

[mazimkhan]

@adbridge Done.